1. Technical Field
The present invention relates in general to a combustion catalyst for diesel and in particular to a catalyst containing an over-based magnesium compound combined with a soluble iron compound. Such catalyst is particularly useful in compression-ignited reciprocating engines operating on diesel fuel.
2. Description of the Prior Art
The effects of various metals listed above are known to improve combustion in boilers and combustion turbines and metals are known to vary ash quality. Useful first row transition metals from the periodic table include iron, manganese and copper. Also, various alkaline earth metals (barium, calcium) and others such as cerium, platinum and palladium have been tested. Manganese is most widely used as a combustion catalyst in boilers with residual oil, which often contains fuel contaminants, such as vanadium. Platinum and palladium, generally found in catalytic converters, are quite expensive. Manganese, when used alone, also forms low melting deposits and negates effects of magnesium on control of vanadium/sodium/calcium/potassium deposits. Iron catalyzes sulfur trioxide formation from sulfur dioxide increasing “cold end” corrosion (exhaust area) and sulfuric acid “rain” problems. Copper is less effective than either iron or manganese. Calcium forms tenacious deposits with other contaminant metals. Barium forms toxic salts. Cerium is not considered effective because of its higher elemental weight. These metals have been demonstrated to reduce smoke by no more than 50% at concentrations of up to about 50 PPM on a weight/weight basis by Environmental Protection Agency Test Method 5 (EPC M-5). Stability of the metal molecules is also not at issue and therefore not tested in boiler and turbines.
Combustion turbine engines are known to produce an excessive amount of smoke emissions and particulate matter during the start-up cycle due to unstable combustion, particularly when kerosene fuels are used. This can be due to large-sized fuel droplets resulting in inefficient combustion. Oil-soluble iron compounds reduce smoke emission from combustion turbine exhausts by up to 80% at iron concentrations of up to 30 PPM when such engines are operated on liquid petroleum fuels. This has been demonstrated in a combustion turbine engine, such as a Westinghouse Model D501-F 150 MW engine. An iron oxide dispersion product is known to reduce smoke emissions in combustion turbine engines. The dispersion product reached maximum smoke reduction at 55 ppm iron (Fe) as compared with an oil soluble product that reached a maximum reduction at 30 ppm Fe. This can be attributable to the difference between an oil-soluble solution of the iron product at the molecular level compared with a dispersion product having an average particle size of 0.5 to 1.0 micrometer.
Dispersion-type manganese (Mn) and iron (Fe) compounds have been used to reduce smoke emissions in low-speed (150-400 rpm) marine diesel engines. However, these compounds produce solid material in the gaseous phase. Marine diesel engines are capable of tolerating such gaseous phase solid materials because such engines have large piston and bore size tolerances as compared with higher speed diesel engines. Moreover, marine diesel engines consume large amounts of crankcase oil in the combustion process, which may help to reduce solid material accumulation. Medium (450-1,000 rpm) and high speed (>1,000 rpm) engines cannot tolerate high levels of contamination of crankcase oil from combustion products. However, dispersion-type manganese and iron compounds have not been shown to have any synergistic relationship for combustion catalysis.
Over-based magnesium (Mg) compounds are known in the art for converting trace metal contaminants into high melting compounds and reducing deposits in combustion turbine engines operated by liquid petroleum fuels containing trace metal contaminants such as vanadium, lead, sodium, potassium and calcium. These contaminants form low melting point corrosive deposits on hot metal parts in reciprocating engines, such as low-speed marine diesel engines. Magnesium is known to form high-melting salts with vanadium, sodium and other fuel contaminants. As a result, over-based magnesium compounds are used alone as fuel additives for compression-ignited reciprocating engines to reduce the effects of these contaminants. For example, an over-based magnesium compound has been used alone in a Wartsilla V32 18 cylinder 8 MW stationary diesel engine, to alleviate the effects of deposits and corrosion from the residual oil fuel used. However, there are no known magnesium-containing fuel additives for diesel engines, which reduce smoke and particulate emissions.
Heretofore, there has not been a fuel additive for reducing smoke and particulate emissions from high speed (>1,000 rpm), high-compression reciprocating engines, such as diesel engines. There is a need for a fuel additive that includes a combustion catalyst to reduce smoke and particulate emissions from bus, truck and automobile diesel engines operating on diesel fuels, such as refined No. 2 grade fuels.
The present invention meets this and other needs. It is an object and goal of the current invention to reduce smoke emissions and particulate matter from high-speed, high-compression reciprocating engines, such as diesel engines.
It is an object and goal to create an additive that does not result in the formation of precipitates. It is an object and a goal to create a soluble iron additive that remains stable during the combustion process. It is an object and a goal to create an additive for hydrocarbon fuel that reduces level of NOx produced.